Despite being one of the leading architects of the Iraq War, former Defense Secretary Donald Rumsfeld has taken a drastic shift in his views, recently admitting that he was apprehensive about the 2003 U.S. Iraq invasion when he first heard the idea.

Rumsfeld, who served as the Secretary of Defense under the Bush Administration from 2001 to 2006, told the Times of London that former President George W. Bush was wrong and "unrealistic" to try to build democracy in the country.

"I'm not one who thinks that our particular template of democracy is appropriate for other countries at every moment of their histories. The idea that we could fashion a democracy in Iraq seemed to me unrealistic. I was concerned about it when I first heard those words," Rumsfeld told the Times of London last weekend.

The striking admission marks a sharp contrast to his stance on the war while he was still in office.

Rumsfeld, who was one of the Iraq War's biggest defenders, also criticized western governments for their current failure to deal with Islamic terror groups like the Islamic State, or ISIS.

"The movement for a caliphate, the movement against nation states is central and fundamental. And no one's talking about it," he said.

Rumsfeld said western leaders have minimized the threat of ISIS although extremists continue to recruit foreign fighters to join their ranks in Iraq and Syria and help them establish a caliphate.

"If leaders aren't willing to do it, why the hell should a guy with a wife and kids in the community put himself at risk?" he asked, describing the fight ahead as "more like the Cold War" -- won with ideas, not "bullets."

Rumsfeld went on to warn that NATO and the United Nations may be ill prepared to deal with threats from Islamic extremists.